The semiconductor integrated circuit (IC) industry has experienced rapid growth. Over the course of the growth, functional density of the semiconductor devices has increased with decrease of device feature size or geometry. The scaling down process generally provides benefits by increasing production efficiency, reducing costs, and/or improving device performance. However, such scaling down has also increased complexity of the IC manufacturing processes.
With the demands on shrinking geometry of ICs, a three dimensional transistor, such as a fin-like field-effect transistor (FinFET), has been introduced to replace a planar transistor. However, device performance and yield of such FinFET are still not satisfactory in advanced applications of technology. Therefore, improvements in structures and methods of forming a FinFET with better device performance continue to be sought.